1. Field of the Invention
The present invention relates in general to a control device for controlling operation of an internal combustion engine, and more particularly to a valve timing control device which controls or varies an open/close timing of intake and/or exhaust valves of the internal combustion engine in accordance with an operation condition of the engine.
2. Description of the Related Art
In order to clarify the task of the present invention, one valve timing control device of an internal combustion engine will be briefly described, which is shown in Laid-open Japanese Patent Application (Tokkai-hei) 10-153104.
In the valve timing control device of the publication, a timing pulley driven by a crankshaft of the engine is rotatably disposed around a shaft member which is integrally connected to a camshaft. A so-called xe2x80x9crelative rotation angle control mechanismxe2x80x9d is arranged between the timing pulley and the shaft member. The relative rotation angle control mechanism comprises generally a piston member which is axially movably connected to the timing pulley while being suppressed from rotating about an axis thereof relative to the timing pulley, a first helical gear which is formed on a cylindrical inner surface of the piston member, a second helical gear which is formed on a cylindrical outer surface of the shaft member and meshed with the first helical gear and an electric actuator which moves the piston member axially. The electric actuator comprises an electromagnet and a return spring. That is, by moving the piston member forward or rearward to a desired position by the electric actuator, a relative rotation angle between the timing pulley and the shaft member is controlled or varied.
However, due to the nature of the mutually meshed two helical gears, a considerable meshing resistance is inevitably produced by them, which tends to deteriorate a smoothed angle change of the shaft member relative to the timing pulley. If, for reducing the meshing resistance, the two helical gears are so arranged that mutually meshed teeth of the two helical gears have a certain gap kept therebetween, noises would be produced due to variable torque of the camshaft. Furthermore, if, for reducing the meshing resistance, the inclination angle of the helical teeth of each gear is increased, the size of these helical gears would become increased, which brings about a bulky construction of the relative rotation angle control mechanism.
It is therefore an object of the present invention to provide a valve timing control device of an internal combustion engine, which is free of the above-mentioned drawbacks.
That is, according to the present invention, there is provided a valve timing control device of an internal combustion engine, which is compact in size and assures a smoothed rotation angle change of the shaft member relative to the timing pulley without producing uncomfortable noises.
According to a first aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a relative rotation angle control mechanism through which the drive and driven rotation members are coaxially connected, the relative rotation angle control mechanism having a movable control member which, when actuated, varies a relative rotation angle between the drive and driven rotation members in accordance with an operation condition of the engine, the relative rotation angle control mechanism comprising a radial guide provided by one of the drive and driven rotation members; the movable control member guided by the radial guide in a manner to move in a radial direction with respect to the given axis; a link which links the movable control member to a given portion of the other of the drive and driven members, the given portion being positioned away from the given axis in a radial direction; an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members; a spiral guide provided by the intermediate rotation member to guide the movement of the movable control member, so that rotation of the intermediate rotation member relative to the radial guide induces a radial movement of the movable control member; and a sliding resistance reducing structure arranged between the movable control member and the intermediate rotation member to reduce a sliding resistance produced when the movable control member is moved.
According to a second aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a radial guide provided by one of the drive and driven members; a movable control member guided by the radial guide in a manner to move in a radial direction with respect to the given axis; a link liking the movable control member to a given portion of the other of the drive and driven members, the given portion being positioned away from the given axis in a radial direction; an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members; a spiral guide groove provided on one surface of the intermediate rotation member; a semi-spherical recess formed in the movable control member, the recess facing the one surface of the intermediate rotation member; and a rolling ball rotatably and slidably engaged with both the spiral guide groove and the semi-spherical recess.
According to a third aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a radial guide provided by one of the drive and driven members; a movable control member guided by the radial guide in a manner to move in a radial direction with respect to the given axis; a link liking the movable control member to a given portion of the other of the drive and driven members, the given portion being positioned away from the given axis in a radial direction; an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members; a spiral guide groove provided on one surface of the intermediate rotation member, the spiral guide groove having a semi-circular cross section; a semi-spherical recess formed in the movable control member, the recess facing the one surface of the intermediate rotation member; and a rolling ball rotatably and slidably engaged with both the spiral guide groove and the semi-spherical recess, at least one of the spiral guide groove and the semi-spherical recess having a radius of curvature that is greater than that of the rolling ball.
According to a fourth aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a radial guide provided by one of the drive and driven members; a movable control member guided by the radial guide in a manner to move in a radial direction with respect to the given axis; a link liking the movable control member to a given portion of the other of the drive and driven members, the given portion being positioned away from the given axis in a radial direction; an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members; a spiral guide groove provided on one surface of the intermediate rotation member; a semi-spherical recess formed in the movable control member, the recess facing the one surface of the intermediate rotation member; a rolling ball rotatably and slidably engaged with both the spiral guide groove and the semi-spherical recess; and a biasing structure which biases at least one of the intermediate rotation member and the movable control member toward the rolling ball.
Other objects and features of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings.